The science bit

ST*

From some notes and searches:

The sleep cycle.

Stage 1 - This makes up for 4-5% of your sleep. It is light, muscle activity slows down, although there is some occasional twitching.

Stage 2 – This makes up for 45-55% of your sleep, and it is where your breathing pattern and heart rate slows. There is also a decrease in your body temp.

Stage 3 – This makes up for 4-6% of your sleep, and is regarded as the deep sleep. At this point you will stage to generate small delta waves.

Stage 4 – This makes up for 12-15% of your cycle, and is regarded as the very deep sleep stage. There is a rhythemic breathing pattern, limited muscle activity. Now producing strong delta waves.

Stage 5 – This makes up for 20-25% of your cycle, REM, brainwaves speed up and dreaming occurs. Muscles relax, and heart rate increases, breathing is rapid and shallow.

Brain Waves

Our brains cycle through four types of brain waves, referred to as delta, theta, alpha and beta. Each type of brain wave represents a different speed of oscillating electrical voltages in the brain.

Delta is the slowest (zero to four cycles per second) and is present in deep sleep.

Theta (four to seven cycles per second) is present in stage one when we're in light sleep.

Alpha waves, operating at eight to 13 cycles per second, occur during REM sleep (as well as when we are awake).

Beta waves, which represent the fastest cycles at 13 to 40 per second, are usually only seen in very stressful situations or situations that require very strong mental concentration and focus. These four brain waves make up the electroencephalogram (EEG).

iFight

Thanks, nice work, very interesting

Black Swan

Stage 5 is from 20 to 25 percent? Whoa! It's seems when you dream that most of the time asleep is taken by it, when in reality it's considerably less. I would wonder if this percentage can be manipulated to be increased or decreased using some kind of techniques, and if so, what would be those techniques, as well as the consequences?

ST*

That is a good question. A lot of people believe with the use of relaxation techniques they can greatly improve the quality of their sleep, more rested. Might check that out actually.

meowCat

This article in the Health Journal says at the end that these percentages change during the course of the night:

"As the night progresses, REM sleep periods increase in length while deep sleep decreases. By morning, people spend nearly all their sleep time in stages 1, 2, and REM."

Also, ST*, could you give a few references?